Articulation angle sensor

ABSTRACT

Sensors (170, 172) for sensing articulation angle (AA) and/or a time derivative thereof (dAA/dt, d 2  AA/dt 2 ) for a trailer anti-swing control system are provided. In the preferred embodiments, at least the active transducers of the sensors are mounted to the tractor (12) subvehicle of the articulated vehicle system (10).

BACKGROUND OF THE INVENTION

1. Related Applications

This application is related to U.S. application Ser. No. 454,110 titledTrailer Anti-Swing System and Method, U.S. application Ser. No. 454,109titled Trailer Brake Anti-Swing System and Method, U.S. application Ser.No. 454,609 titled Tractor Trailer Anti-Trailer Swing System and MethodU.S. application Ser. No. 454,095 titled Anti-Trailer Swing Control andU.S. application Ser. No. 454,574 titled Tractor Trailer ArticulationControl System and Method, all assigned to the assignee of thisapplication and filed the same day (Dec. 10, 1989) as this application.

2. Field of the Invention

The present invention relates to a control system/method for controllingthe braking force applied to the brakes of a towed subvehicle in anarticulated vehicle system, such as the semitrailer subvehicle in atractor-semitrailer system, to prevent, arrest or to minimize andquickly recover from, the condition known as trailer brake inducedtrailer swing.

More particularly, the present invention relates to a trailer anti-swingsystem for an articulated vehicle wherein at least the active transducermembers of the means for sensing articulation angle are mounted entirelyon the tractor.

3. Description of the Prior Art

Brake control systems for all types of vehicles, including heavy dutytractor-semitrailer trucks, to improve the stopping and vehiclestability thereof are, of course, well known in the prior art.

Brake systems of the anti-lock type, for all types of vehicles, are wellknown in the prior art. Briefly, these systems operate to maintainvehicle stability (i.e. acceptable transverse coefficient of friction ofbraked wheels) by maintaining the longitudinal slip of the braked wheelswithin predetermined limits. This usually requires modulating thebraking forces on an individual wheel and/or individual axle basis tomaintain at least some wheel rotation.

Examples of prior art anti-lock brake systems ("ABSs") may be seen byreference to U.S. Pat. Nos. 3,767,270; 3,768,872; 3,854,556; 3,893,696;3,929,383; 3,929,382; 3,966,267; 4,392,202 and 4,591,213, thedisclosures of all of which are hereby incorporated by reference.

Brakes systems which control braking to achieve a driver demand, sensedriver demand in a "brake-by-wire" manner, sense coefficient of frictionand modify brake forces accordingly, sense load on a wheel and modifybraking effort accordingly, sense wheel slip and/or use electronicsignals to achieve trailer brake response are also disclosed in thePrior art as may be seen by reference to U.S. Pat. Nos. 4,140,352;4,327,414; 4,494,199; 4,512,615; 4,545,240; 4,591,213; 4,606,586;4,616,881; 4,648,663 and 4,768,840, the disclosures of which are herebyincorporated by reference.

Brake systems for heavy duty articulated vehicles such astractor-semitrailer trucks are difficult to design as the loading andmaintenance will vary in a truck, such as the loading on the tractor ofa tractor-trailer which may comprise a tractor only, a tractor with anempty or lightly loaded trailer or a tractor with a heavily loadedtrailer.

Further, the tractor-semitrailers are, by their nature, capable ofexhibiting certain unstable dynamic behaviors known as jackknife andtrailer swing, each of which has its own characteristic cause, effectand appropriate sequence of corrective action. Jackknife is sometimescalled "tractor brake caused jackknife" while trailer swing is sometimescalled "trailer brake caused jackknife".

The dynamics of undesirable trailer articulation events, such as ajackknife event, are discussed in SAE Paper No. 710045, the disclosureof which is hereby incorporated by reference.

Various systems to prevent or minimize trailer swing have been proposed.These include mechanical devices such as chains or variable pivotresistance devices and also wheel speed sensors and anti-lock controlson the trailer per se. Examples of these prior art devices may be seenby reference to U.S. Pat. Nos. 3,618,983; 3,810,521; 3,894,773;4,023,864, 4,405,145 and 4,620,717 the disclosures of which are herebyincorporated by reference.

The prior art devices were not satisfactory as the mechanical deviceswere somewhat slow to react, hindered required articulation duringnormal operation, required specially configured/equipped trailers and/ordid not allow for a recovery from the locked-in condition. The anti-lock(ABS) type systems were not totally satisfactory as most existingtrailers do not have ABS equipment, tractors are often driven with avariety of trailers and thus even if a trailer is provided with ABSequipment, it may not be compatible with the tractor ABS, providing allexisting and future trailers with ABS equipment is prohibitivelyexpensive and, under certain conditions, undesirable trailerarticulation may occur in the absence of the wheel lock conditionssensed and reacted to by existing ABSs.

SUMMARY OF THE INVENTION

In accordance with the present invention, many of the drawbacks of theprior art have been overcome or minimized by the provision of a traileranti-swing control system/method which is suitable for use withsemitrailers equipped with standard (i.e., non-ABS) brake controls andwill control the pilot or actuation pressure supplied to the trailerbrake system to halt sensed trailer swing initiation and allow thetrailer to safely recover therefrom.

The above is accomplished by providing, preferably entirely on thetractor, an ABS type valve located on the tractor upstream from the gladhand connection, sensors for sensing and/or providing signals allowingthe calculation of tractor/trailer articulation angle ("AA"), rate ofchange of articulation angle ("dAA/dt") and rate of change of rate ofchange of articulation angle (37 d² AA/dt²) and a control device,preferably microprocessor based, for receiving input signals, processingsame in accordance with predetermined logic rules and issuing commandoutput signals to control the trailer brake ABS type valve.

For a more responsive control, higher order time derivatives ofarticulation angle may be used. The "ABS type valve" should have thefunctions of lowering pressure to release the trailer brakes, holdingthe pressure at a low value to maintain brakes released, then reapplyingthe brakes in a controlled manner to a desired reapply pressure, allindependent of the degree of braking effort demanded by the vehicledriver.

Accordingly, it is an object of the present invention to providearticulation angle sensors for an improved trailer brake control systemfor the trailer subvehicle of an articulated vehicle system, such as thetrailer of a tractor-semitrailer truck system, which is operative todetect the onset of and prevent, or to minimize and allow recovery from,a trailer swing condition. Preferably, all of the control and sensingcomponents, at least the active control and sensing components, will bemounted on the tractor subvehicle and will allow use of the controlsystem with any standardly equipped trailer subvehicle.

This and other objects and advantages of the present invention willbecome apparent from a reading of the detailed disclosure of thepreferred embodiments taken in connection with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a conventional heavy dutytractor-semitrailer truck articulated vehicle.

FIG. 2 is a schematic illustration of a tractor mounted brake controlsystem including an anti-lock brake system, and also incorporating thetrailer anti-swing control system of the present invention.

FIG. 3 is a schematic illustration of a standard trailer brake systemwhich may be utilized with the trailer anti-swing brake control systemof the present invention.

FIG. 4 is an enlarged, fragmentary, schematic illustration of the kingpin/fifth wheel pivotal connection between a tractor and a semitrailerillustrating the angular relationship defined by the articulation angle.

FIG. 5 is a graph illustrating the trailer brake applied pressure versustime curve(s) for the trailer anti-swing control system/method of thepresent invention.

FIG. 6 is a schematic illustration of the occurrence of an uncontrolledtrailer swing event.

FIG. 7 is an illustration of a floating rotor potentiometer type ofarticulation angle sensor for the control system/method of the presentinvention.

FIG. 7A is a partial sectional view of the sensor of FIG. 7.

FIG. 8 is an illustration of an ultrasonic distance sensor typearticulation angle sensor for the control system/method of the presentinvention.

FIG. 9 is a schematic illustration of a magnetic field direction sensortype of articulation angle sensor for the control system/method of thepresent invention.

FIG. 9A is a partial sectional view of the sensor of FIG. 9.

FIG. 9B is a symbolic representation of a flux gate magnetometer used asa rotational position sensor.

FIG. 10 is a schematic illustration of a glad hand transmitter typearticulation angle sensor for the control system/method of the presentinvention.

FIG. 11 is a schematic illustration, in the form of a flow chart, of thetrailer anti-swing control system/method of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The articulation angle sensors for a trailer anti-swing controlsystem/method of the present invention are applicable to articulatedmultiple vehicle systems such as the tractor-semitrailer system 10illustrated in FIG. 1. Briefly, as is well known to the Prior art, thetractor-semitrailer system 10 comprises a tractor 12 and a semitrailer14 attached thereto by a connecting means 16 which comprises the wellknown fifth wheel 34 fixed to the tractor for selective engagement witha king pin fixed to the trailer. The tractor typically comprises a pairor tandem set of rear drive axles 36 and 38 and a front steer axle 40.The trailer 14 typically comprises a tandem pair of non-steerable,non-driven trailer axles 42 and 44. Typically, but not necessarily, thefront axle 40 will have non-driven steerable wheels The tractor and/orthe trailer may be equipped with single axles or three or more axles.

The ability to utilize fifth wheel/king pin connections to relativelyquickly and easily couple or connect standardly equipped tractors tostandardly equipped semitrailers in an articulated or pivoted mannerprovides the well appreciated advantages of commercial and operationalflexibility as well as increasing the maneuverability of the vehicles.However, under certain conditions, often associated with braking whilenegotiating a curve or a turn, one or both of the tractor-semitrailersubvehicles may lose transverse stability resulting in a condition ofuncontrolled excessive articulation, i.e. jackknife or trailer swing.Tractor-semitrailer uncontrolled excessive articulation is generallyconsidered to consist of two distinct types of events, namely"jackknife" and "trailer swing", both of which may lead to catastrophicresults.

Jackknifing, which is considered to be the most severe and leastcorrectable type of uncontrolled excessive trailer articulation event,usually results from the tractor subvehicle, usually the tractorsubvehicle drivewheels, losing transverse stability, often whilecornering, which lack of stability is quickly compounded by the oftenrelatively many times greater inertia imposed by the trailer. The othertype of uncontrolled excessive trailer articulation event, trailerswing, is generally the result of the trailer wheels, 42 and 44, losingtransverse stability, usually while cornering, resulting in the trailerswinging radially outwardly relative to the center of the curve beingnegotiated which may result in the trailer swinging into adjacenttraffic lanes with the obvious potential for catastrophic resultstherefrom.

Trailer swing events often occur less rapidly than the jackknife events,and upon sensing conditions indicative of the advent of a trailer swingcondition corrective action may be taken of the trailer brakes tominimize the extent of trailer swing and to cause the trailer to resumeits tracking condition.

As is very well known, decreasing the slip of a tire will dramaticallyincrease the transverse coefficient of friction thereof. Accordingly,trailer swing induced by locked or almost locked trailer brakes, ifsensed at the onset or initiation thereof, may be arrested or reduced byincreasing the transverse stability of the trailer wheels by releasingthe brakes thereof and allowing the wheels to roll up to or towardsvehicle speed. The schematic illustration of an extreme trailer swingevent may be seen by reference to FIG. 6 wherein the trailer at theright-hand portion of the illustrated curve has swung totally out of itslane. The purpose of the control system/method of the present inventionis to prevent the occurrence of, or to minimize the extent of, trailerbrake induced trailer swing events.

The trailer anti-swing control system/method of the present invention ispreferably utilized with a tractor 12 fully equipped with an ABS systemand a trailer 14 equipped with a standard, i.e. non-ABS, brake system.However, the control of the present invention would also providebenefits if utilized with a vehicle having both tractor and trailer ABSas, under certain conditions, undesirable trailer articulation may occureven though the vehicle wheels have not locked up to the extent that isnecessary to cause corrective action by currently existing ABS systems.Additionally, although not preferred, the trailer anti-swing controlsystem/method of the present invention will provide a degree of improvedvehicle stability when utilized on a tractor trailer system whereinneither the tractor nor the trailer was provided with an ABS logiccontrol.

As stated above, the purpose of the present invention is to Prevent orminimize trailer brake induced trailer swing events while the occurrenceof jackknife events is minimized by the provision of the tractor ABScontrol logic and devices.

A braking system for the tractor 12 of an articulatedtractor-semitrailer system 10 which utilizes the trailer anti-swingcontrol system/method of the present invention may be seen by referenceto FIG. 2. It is noted that while the braking system for tractor 12illustrated in FIG. 2 is of the "brake by wire" type, the presentinvention is equally applicable to other types of brake controls and ABSsystems.

Briefly, as is well known in the prior art, tractor 12 includes a frontsteer axle 40, which is usually not driven, and a tandem pair of reardrive axles comprising front-rear drive axle 36 and rear-rear drive axle38. Wheels 140 and 142 are associated with the rear-rear drive axle 38,wheels 144 and 146 are associated with the front-rear drive axle 36 andwheels 148 and 150 are associated with the front steer axle 40. The reardrive axles, 36 and 38, are driven by engine 46 through transmission 48and driveline 50.

Air actuated brake 60, 62, 152, and 154 are provided for retarding therotation of wheels 144, 146, 140 and 142, respectively. The rear brakes60, 62, 152 and 154 are, as is well known in the prior art, of the samesize and type as likewise are the front brakes 64 and 66 which areprovided for selectively braking the rotation of front steer drive axlewheels 148 and 150, respectively. In the system illustrated, the brakesare air actuated brakes of one of the well known types, such as the "S"cam actuated brake type or the air disc brake type, the details of whichare well known in the prior art and may be seen in greater detail byreference to U.S. Pat. Nos. 4,476,968 and 4,457,407, the disclosures ofboth of which are hereby incorporated by reference. While all of thefront brakes and all of the rear brakes should be of the same size andtype, it is not necessary, and is not preferable, that the front andrear brakes be of the same size. Compressed air for actuating the brakesis supplied from a plurality of supply tanks 68, only one of which isshown, which supply tanks are provided with compressed air from thevehicle onboard compressor (not shown) or the like.

The braking system includes a control unit 70, which for purpose offlexibility and responsiveness is preferably an electronicmicroprocessor based control unit having means 72 for receiving aplurality of input signals, means for processing input signals inaccordance with predetermined logic rules, and means 74 for issuingcommand output signals to various system operators.

A sensor 76 senses the operator's displacement of a brake pedal 78 toprovide an input signal indicative of the driver's demand or vehiclestopping effort. Sensors of this type are known in the prior art and maybe seen by reference to above-mentioned U.S. Pat. Nos. 4,140,352;4,327,414 and 4,512,615. Typically, such transducers will sense thedisplacement of and/or force applied to the brake pedal 78 and willprovide an output signal proportional thereto. As indicated above, thepresent invention is equally applicable to more conventional brakesystems wherein the amount of braking effort is controlled by a wellknown treadle valve. To provide tractor ABS operation, wheel speedsensors 160, 162, 98, 100, 102, 104 are provided for providing inputsignals indicative of the rotational speed of wheels 140, 142, 144, 146,148 and 150, respectively.

The central processing unit 70 will, as is well known in the ABS priorart, process the input signals in accordance with predetermined logicrules to generate command output signals to the front control valve 108and the rear control valve 168. Briefly, control valve 108 is connectedto the supply tank 68 through supply line 110, and, in accordance withthe command output signals from CPU 70, independently pressurizes theconduits 116 and 118 leading to air brakes 64 and 66, respectively. Rearcontrol valve 168 is also connected to supply tank 68 through supplyline 110 and, in accordance with command output signals from CPU 70,individually provides pressurized fluid via branch conduits to the rearaxle brakes 60, 62, 152 and 154. Accordingly, it may be seen that thebraking efforts of each of the tractor wheels may be individuallycontrolled for ABS purposes in a closed loop manner in response tocommand output signals generated by the CPU 70 in response to the inputsignals received and processed thereby, as is known ABS technology.

To provide the trailer anti-swing control system/method of the presentinvention, the tractor braking system is also provided with one or moresensors 170 and 172, preferably mounted on the tractor such as at thefifth wheel 34, for providing input signals to CPU 70 indicative ofand/or allowing the calculation of the current articulation angle (AA),and of time derivatives thereof such as the rate of change ofarticulation angle (dAA/dt) and the rate of change of the rate of changeof articulation angle (d² AA/dt²). Of course, sensors may be providedfor directly sensing one or more of the time derivatives of articulationangle. In addition, a control valve 174, controlled by command outputsfrom CPU 70, will provide pilot or controls to the standard trailerbrake system control valves. Preferably, the control valve 174 islocated on the tractor just upstream of one of the gladhand connectors206. Valve 174 may be replaced by a standard treadle valve having anoutput proportional to the displacement of brake pedal 78 and an ABStype valve connected in series downstream therefrom.

Applicant's convention for the measurement of articulation angle, andthe first and second derivatives thereof with respect to time, andvarious sensing means for sensing same will be described in greaterdetail below.

Referring now to FIG. 3, a prior art standard trailer brake system (i.e,non-ABS) is illustrated. Briefly, the trailer includes a king pin 176for selective engagement and disengagement to the tractor fifth wheel 34as is well known in the prior art. The trailer includes a supply tank178 connected to the tractor air system by means of a fluid connection180. Trailer axles 42 and 44 support trailer wheels 182, 184, 186 and188, each of which is provided with an air brake actuators or chambers190, 192, 194 and 196, respectively. Typically, all of the trailerbrakes are controlled at the same pressure by means of a relay valve 198which has an inlet 200 connected to the trailer supply tank 178 and apilot valve portion 202 for receiving a pilot air signal from thetractor air system by means of connector 204. Each of the trailer brakesis actuated at approximately the same pressure from a single output 208from a pilot controlled relay valve 198.

Connector 204 is designed for connection with connector 206 on thetractor Briefly, the connectors 204 and 206 and likewise connector 180and its associated connection with a vehicle air system (not shown) formthe fluid connection commonly known as the "gladhand".

Applicant's convention, which will be used throughout this application,for the measure of the articulation angle (AA) may be best understood byreference to FIG. 4 wherein the pivot axis between the tractor 12 andtrailer 14 defined by the fifth wheel 34 and king pin 176 connection isviewed from the top of the vehicle, i.e. with the trailer extendingrearwardly from left to right as shown in FIG. 4. The articulation anglebetween the tractor and trailer, AA, is defined as the included anglebetween the longitudinal axis 200 of the tractor 12 passing through theking pin/fifth wheel pivot axis and the longitudinal axis 202 of thetrailer 14 passing through the fifth wheel/king pin pivot axis Thearticulation angle AA is measured from the tractor longitudinal axis 200to the trailer longitudinal axis 202 and is assigned a positive value inthe counterclockwise direction and a negative value in the clockwisedirection. In the example shown in FIG. 4, accordingly, the articulationangle AA would have a positive value under applicant's herein definedconvention.

Referring to FIG. 6, as vehicle 10 moves generally from left to right asseen in FIG. 6 around the course defined by the curved lane, it may beseen that the wheels of the trailer 14 lose transverse stability and,under the influence of centrifugal force, and a retarding force providedby the tractor itself the trailer 14 will pivot about the king pin suchthat articulation angle will typically pass through zero then changesigns as the swing out phenomenon progresses. In a trailer swing event,the trailer 14 swinging out of its lane is a potentially hazardousoccurrence. This is an example of the type of trailer swing event thatthe anti-trailer swing control method and control system of the presentinvention is intended to prevent, arrest or to minimize and allow rapidrecovery from.

The loss of transverse stability of the trailer wheels sufficient toresult in a trailer swing event as illustrated in FIG. 6, is typicallyassociated with an application of the trailer brakes resulting in wheelslip exceeding a desirable value and/or total wheel lock. To prevent theoccurrence of a trailer brake induced trailer swing event, or to arrestand minimize the extent thereof and to allow quick recovery therefrom,it is desirable that conditions indicative of incipient or actual onsetof trailer swing be quickly sensed and that the vehicle brake systemreact thereto by releasing the trailer brakes allowing the trailerwheels to roll back up towards vehicle speed to minimize the slip andincrease the transverse coefficient of friction, and thus increase thecentripetal force of the trailer wheels.

The trailer anti-swing control method and system of the presentinvention is operable to sense conditions indicative of incipient, orthe onset of, a trailer brake induced trailer swing event by the sensingand/or calculating, at a time when the vehicle brakes are applied, atleast one or more of the articulated vehicles' articulation angle, and atime derivative of articulation angle such as the first derivative ofarticulation angle with respect to time and/or the second derivative ofarticulation angle with respect to time. It is important to sensetrailer swing at the initiation or onset, i.e. prior to the trailerswinging towards an almost zero articulation angle position, to havesufficient time to arrest and/or minimize the condition. It is alsoimportant to distinguish trailer swing from jackknife as differentcorrective responses are required.

Briefly, one method of sensing an incipient trailer swing event is thesensing of conditions, when the brake pedal is applied, wherein thearticulation angle (AA) and a time derivative thereof, such as the firstderivative of the articulation angle with respect to time (d² AA/dt²)are of opposite signs (which is an indication that the trailer 14 isswinging outwardly from the center of a curve which thetractor-semitrailer vehicle is traversing) and the absolute value of thesecond derivative of the articulation angle with respect to time (d²AA/dt²) exceeds the absolute value of a predetermined referenceindicating that the trailer is pivotally accelerating rapidly radiallyoutwardly from the center of the curve being traversed by thearticulated vehicle.

Upon sensing these conditions, the control logic of the presentinvention will declare the existence of conditions indicative of anincipient trailer swing event and will release the trailer brakes for agiven period of time (T) selected to allow the trailer wheels to rollback up towards vehicle speed to increase the transverse stabilitythereof and preferably minimize or eliminate the trailer swing and allowthe trailer wheels to again track on the curve. After the predeterminedperiod of time, trailer brakes will be reapplied at a rate (R) which maybe fixed or may vary with measured system variables to a reapplicationpressure (P) which is preferably a function of the value of the firstand/or second derivative of articulation angle with respect to time atthe onset of the trailer swing event. The brakes will be maintained atthis pressure peak until such time as the braking event is terminated,i.e., the operator removes his foot from the brake pedal, at which pointtrailer brakes will again be controlled by the treadle valve until suchtime as incipient trailer swing is again sensed. The application ofpressure to the trailer brakes is controlled by trailer anti-swingcontrol valve 174 which varies the Pressure applied to the pilot portion202 of the trailer relay valve 198. A graphic illustration of thepressure applied to the trailer brakes to minimize and recover from asensed incipient trailer swing event may be seen by reference to FIG. 5.

Referring to FIG. 5, at point 204 to point 206 the vehicle brakes arenot applied. At point 206, the vehicle operator has fully depressed thetreadle valve or brake pedal 78 causing the relay valve 198 in thetrailer, under the control of trailer brake control valve 174, to applythe trailer brakes with a high pressure as seen in point 208. If theoperator continues to request a relatively high braking effort, trailerbrakes will remain applied at a relatively high level from point 208 topoint 210. For purposes of this example, at point 210 it will be assumedthat the input signals processed by the CPU controller 70 indicate theexistence of an incipient trailer swing event. The CPU 70 will thenissue command output signals to the trailer brake control valve 174causing the trailer brakes to be released as may be seen at point 212.The trailer brakes will be maintained in the released position for apredetermined period of time T which is selected as a time sufficient toallow the trailer wheels to roll back up to near vehicle speed. Time Tmay be predetermined or may vary with the value of sensed inputs to theCPU. Typically, as the trailer wheels are not provided with speedsensors, this is an empirically predetermined value. Applicant hasdiscovered that a period of time from 0.25 to 1.25, preferably from 0.50to 0.75, seconds is sufficient to allow the trailer wheels to roll backup to approximately vehicle speed allowing the trailer brakes to bereapplied to minimize the stopping distance of the total vehicle 10.

Accordingly, at the end of the predetermined period of time T, i.e., atpoint 214, the trailer brakes are reapplied at a rate R until a pressureP is achieved at point 216, which pressure P is preferably a function ofthe sensed or calculated first and/or second derivative of thearticulation angle at the onset of the trailer swing event. Vehiclebrakes will then be maintained at pressure P until termination of thebraking event. Applicants have discovered that a rate of reapply R equalto about 10 PSI per second is an effective rate to achieve the pressureP as rapidly as possible without resulting in a repeat trailer wheeltransverse loss of stability.

Reapply pressure P and/or the rate (R) of reapply pressure are, asstated above, a function of the dynamics of the trailer swing event assensed by the values of articulation angle, the first derivative andsecond derivative of articulation angle during the trailer swing event.

Briefly, the absolute values of the first and second time derivatives ofarticulation angle during a trailer swing event are indicative of theloading on the trailer and/or the friction coefficient of the road. Themore rapid the change in articulation angle and the rate of change ofthe change of articulation angle, the more lightly loaded is the traileror the lower the coefficient of friction of the road. Accordingly, for arelatively high first and/or second derivative of articulation anglewith respect to time, a relatively lower reapply pressure and rate ofreapplying pressure is desirable while with a relatively lower first,second and/or higher derivative of articulation angle with respect totime, a relatively higher reapply pressure may be applied to the trailerbrakes without fear of causing trailer wheels to again lose transversestability.

A control method utilizing the articulation angle sensors of the presentinvention is symbolically illustrated in a flow chart format byreference to FIG. 11.

An alternate method of sensing the existence of conditions indicative ofthe onset of a trailer swing event is to sense, during a vehicle brakingoperation, that (i) the articulation angle (AA) and the rate of changeof articulation angle (dAA/dt) are in opposite rotational directions and(ii) that the rate of change of articulation angle (dAA/dt) exceeds theabsolute value of a reference value.

Upon sensing such conditions, the CPU 70 will command the controller 174to cause the trailer brakes to be released for a period of time T andthen reapplied at a rate (R) to a reapplication pressure (P) one or bothof which may be functions of articulation angle (AA) and/or rate ofchange of rate of change of articulation angle (d² AA/dt²) either thelatest values or the values at the instant of sensing the conditions.

By way of example, by comparing d² AA/dt² to a yaw reference, which yawreference is preferably a function of the initial value of AA, it may bedetermined if the trailer is relatively heavy or light and/or if theroad is of a relatively high or low coefficient of friction bydetermining if it is of a relatively high or low yaw rotational momentof inertia. As is known, for a more heavily loaded trailer and higherfriction road surface, the reapply pressure and/or the rate ofreapplying the trailer brakes may be higher, to more rapidly stop thevehicle i.e., without inducing transverse instability.

A further alternate method of sensing the onset of a trailer swing eventis to sense during a braking operation, (i) if the articulation angle(AA) and the rate of change of the rate of change of articulation angle(d² AA/dt²) are of opposite signs, (ii) if the absolute value ofarticulation angle is at least equal to a predetermined value (about 1°to 3° ) and (iii) if the absolute value of the rate of change of therate of change of articulation angle exceeds the absolute value of areference value.

As is known, the use of higher order time derivatives of sensedarticulation angle will provide the possibility of earlier sensing of anincipient trailer swing condition, especially for more lightly loadedtrailers and/or lower coefficient of friction road surfaces, while theuse of lower order time derivatives responds somewhat later in time butwill allow a less sensitive, somewhat more reliable determination ofincipient trailer swing, especially for more heavily loaded trailersand/or higher coefficient of friction road surfaces. Accordingly, thevarious logical methods described herein for testing for trailer swingconditions are not considered to be mutually exclusive but may be usedin combination with one another.

A sensing that articulation angle and a time derivative thereof are ofopposite signs, and the time derivative (such as d² AA/dt²) exceeds areference value is indicative that although the vehicle is momentarilyproperly articulated, the trailer is accelerating in such a manner as toswing-out from behind the tractor. If the absolute, value of the timederivative (d² AA/dt²) exceeds the absolute value of the referencevalue, corrective action, as described above, should be taken.

The threshold value, i.e. the reference value, for the absolute value ofd² AA/dt² should be a function of the vehicle turning radius which canbe sensed or calculated by means of a steer angle sensor and/or by meansof comparing the rotational speeds of the tractor wheels, preferably thesteer axle wheels, on the right and left sides of the vehicle.

Various sensing devices for sensing the articulated vehicle articulationangle, first derivative of articulation angle with respect to time,and/or the second derivative of articulation angle with respect to timemay be seen by reference to FIGS. 7-10. Preferably, the various sensingdevices include components, all of which, or at least the active ones ofwhich, are mounted on the tractor 12 of the tractor trailer vehicle 10.

Referring to FIG. 7, a fifth wheel assembly 34 is modified by theprovision of two rollers, preferably spring loaded floating rollers 220and 222 which are associated with potentiometers or the like and whichwill be caused to rotate by pivotal movement of the tractor relative tothe trailer to provide input signals indicative of articulation angleand/or the first or second derivatives thereof with respect to time.

Preferably, a pair of rollers 220 and 222 are utilized so thatnonrotational movement of the king pin 176 in the fifth wheel 34 can beisolated and disregarded by the common mode method. Preferably, the axesof rotation 270 of the rollers 220 and 222 are coaxial and pass throughthe king pin fifth wheel pivot axis.

As may be seen by reference to FIG. 7A, the rollers are preferablyrubber coated to provide a resilient adhesion to the undersurface of thetrailer carrying the king pin and are carried on struts 272 which arespring 274 biassed upwardly in frame 276 to extend the rollers above theupper surface 34A of the fifth wheel for contact with an undersurface14A of the trailer adjacent the king pin. Frame 276 is attached to thefifth wheel 34 as by bolts 278. Connectors 280 on strut 272 will providean output for signals from potentiometers 223 which are indicative orproportional to rotation of the rollers.

Referring to FIG. 8, an ultrasonic transceiver 230 is mounted to thetractor 12 and will send and receive ultrasonic signals which bounce offpredetermined surfaces on the trailer 14 provide an indication of thearticulated vehicle articulation angle and/or derivatives thereof.

FIG. 9 illustrates a fifth wheel 34 including a magnet carrying cap 232which will attach to the trailer king pin and which will carry magneticmeans for providing a magnetic sensor for sensing articulation angleand/or one of the derivatives thereof.

As may be seen in greater detail by reference to FIGS. 9A and 9B, amagnet 250 is mounted by a housing 252 to the tractor bed 12 for limitedhorizontal movement and rotational movement about the pivot axis 254.The magnet 250 defines a north 256 and a south pole 258 and is adaptedto magnetically attach to a standard SAE king pin 176 for rotationtherewith where the king pin is received in the fifth wheel 34.

The sensor 260 is preferably of the flux gate magnetometer which allowssensing of relative rotary positions without contact and/or load bearingparts and is relatively tolerant of axial misallignment.

So long as the magnet 250 attached to the monitored part (king pin 176)produces lines of flux 262 which are substantially normal to the axis ofrotation 254, and are parallel at the point of intersection with thecoils 264 of the flux gate, an accurate position signal will beprovided, even if the magnet and the coils are not coaxial.

FIG. 10 illustrates a transmitter associated with the gladhandconnection at the trailer 14 which will send signals to be received by adirection resolving receiver 240 mounted on the tractor 12.

As may be seen, applicant's have provided tractor mounted articulationangle sensors for an improved trailer brake control system/method forcontrolling the trailer brake application forces to prevent, arrest orminimize and provide rapid recovery from trailer swing events.

While the present invention has been described with a certain degree ofparticularity, it is understood that the detailed description of thepreferred embodiments is by way of example only and that numerousmodifications and rearrangements of the components/steps thereof arepossible without departing from the spirit and the scope of the presentinvention as hereinafter claimed.

I claim:
 1. An anti-trailer swing brake control system for articulatedvehicles (10) of the type comprising a tractor (12) and a semitrailer(14) connected at a fifth wheel/king pin articulating connection(34/176) defining a pivot axis (176) about which the semitrailer ispivotable relative to the tractor, an articulation angle (AA) of saidvehicle defined by the included angle defined by a longitudinallyextending axis of the semitrailer passing through said pivot axis (202)relative to a longitudinally extending axis of the tractor passingthrough said pivot axis (200), a tractor brake system, a semitrailerbrake system, a driver operated brake effort demand device (76/78) forproviding a demand signal indicative of the magnitude of the operator'sdemand for vehicle braking, semitrailer brake control means (174)responsive in at least one operating mode for causing the semitrailerbrake system brakes to be applied with an operating force generallyproportional to the magnitude of said demand signal, said control systemcharacterized by:processing means (70) for receiving and processing saiddemand input signal and articulation input signals indicative of atleast one of articulation angle (AA), rate of change of articulationangle (dAA/dt) and rate of change of rate of change of articulationangle (d² AA/dt²) according to predetermined logic rules to detect theexistence of conditions indicative of at least one of incipient andinitial semitrailer swing events and generating signals indicative ofdetection of the existence of said conditions; and sensing means mountedon said tractor for sensing and/or providing signals allowing thecalculation of at least one of articulation angle, rate of change ofarticulation angle and rate of change of rate of change of articulationangle (170, 172), said sensing means comprising at least one rollermember carried by and rotatable relative to said fifth wheel and meansresponsive to rotation of said roller member to provide a control signalindicative of one of articulation angle, rate of change of articulationangle and rate of change of rate of change of articulation angle, saidat least one roller rotatable about an axis (270) extending generallyparallel to an upper surface (34) of said fifth wheel and extendingsubstantially perpendicular to and lying on the same plane as said pivotaxis, said at least one roller biased resiliently upwardly from saidupper surface for contact with an undersurface (14A) of said semitraileradjacent said king pin.
 2. An articulation angle sensor for articulatedvehicles (10) of the type comprising a tractor (12) and a semitrailer(14) connected at a fifth wheel (34)/king pin (176) articulatingconnection defining a pivot axis (176) about which the semitrailer ispivotable relative to the tractor, an articulation angle (AA) of saidvehicle defined by the included angle defined by a longitudinallyextending axis of the semitrailer Passing through said pivot axis (202)relative to a longitudinally extending axis of the semitractor passingthrough said pivot axis (200), said sensor characterized by;a magneticmember (250) defining a north (256) and a south (258) magnetic polecarried (252) by tractor for rotational movement about and limited axialmovement along said pivot axis (254), said magnetic member adapted formagnetic contact and rotational movement with said king pin when saidking pin is received in said fifth wheel for rotational movement aboutsaid pivot axis, and means (260) for sensing rotational movement of saidmagnetic member relative to said tractor and for providing signalsindicative thereof.
 3. The articulation angle sensor of claim 2 whereinsaid means for sensing rotational movement senses changes in the fluxpaths (262) created by said magnetic member.
 4. The articulation anglesensor of claim 3 wherein said means for sensing rotational movementcomprises a flux gate magnetometer.